The Enhanced Communications
Transport Protocol (ECTP) is a transport protocol designed to support
Internet multicast applications running over multicast-capable networks. ECTP
operates over IPv4/IPv6 networks that have the IP multicast forwarding
capability with the help of IGMP and IP multicast routing protocols. ECTP
could possibly be provisioned over UDP. ECTP is targeted to support tightly
controlled multicast connections.

This Recommendation |
International Standard defines the protocol which provides reliability
control in the simplex multicast case, adopting a tree-based approach. Other
Recommendations | International Standards in the ECTP family will define the
QoS management functions for the simplex case and will define reliability
control and corresponding QoS management functions for the duplex case and
the N-plex case.

The sender is at the heart
of multicast group communications. A single sender in the simplex multicast
connection is assigned the role of the connection owner. The connection owner
is responsible for overall connection management by governing connection
creation and termination, connection pause and resumption, and join and leave
operations.

For tree-based reliability control, a hierarchical tree is configured
during connection creation. The sender is the root of the control tree. The
control tree can define a parent-child relationship between any pair of tree
nodes. This tree-based structure can result in local owners occurring at
lower levels in the tree hierarchy as the control structure extends. Each
local owner created becomes the root of its own local control tree. The
connection owner will then be the root of the overall control tree. Error
control is performed for each local group defined by a control tree. Each
parent retransmits lost data, in response to retransmission requests from its
children.